Colloids are ubiquitous in groundwater systems, and understanding their behavior is of critical importance as they can pose a threat to human and environmental health. Extensive research has been conducted to model colloid behavior in fractures leading to the development of a number of analytical solutions, albeit for single fractures. However, the application of these analytical solutions at the network scale has not yet been established; thus, fracture networks are modeled using numerical techniques that are verified in single fractures first. Time domain random walk (TDRW) is a Lagrangian‐based approach originally designed to simulate solute transport in single fractures considering advection, dispersion, and matrix diffusion. The present study develops a modified TDRW approach (MTDRW) to consider colloid‐specific transport mechanisms based on an analytical solution describing colloid behavior in single fractures. The MTDRW approach was validated through simulating the behavior of (i) monodisperse colloids in a synthetic, single fracture with and without matrix diffusion; (ii) polydisperse colloids in a synthetic, single fracture with impermeable matrix; and (iii) monodisperse colloids in a synthetic impermeable fracture network. In all three cases, the MTDRW approach replicated the results of analytical solutions in single fractures and the semianalytical solution in fracture networks. The MTDRW approach is expected to enhance the reliability of colloid transport modeling due to its capacity to simulate the physiochemical heterogeneity across the network. This is required to (i) evaluate the aquifer vulnerability to colloid migration; (ii) predict the aquifer resilience under contamination events; and (iii) develop effective planning, management, and remediation strategies.

中文翻译：

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一种模拟的骨折时胶体行为的改进时域随机行走方法：方法开发与验证

胶体在地下水系统中无处不在，因此了解胶体的行为至关重要，因为它们可能对人类和环境健康构成威胁。已经进行了广泛的研究来模拟裂缝中的胶体行为，从而导致开发了许多分析解决方案，即使对于单个裂缝也是如此。但是，尚未确定这些分析解决方案在网络规模上的应用。因此，使用数值技术对裂缝网络进行建模，该技术首先在单个裂缝中得到验证。时域随机游走（TDRW）是一种基于拉格朗日方法，最初设计用于模拟考虑对流，弥散和基质扩散的单个裂缝中的溶质运移。本研究开发了一种改进的TDRW方法（MTDRW），该方法基于描述单个裂缝中胶体行为的分析解决方案来考虑胶体特定的传输机制。通过模拟（i）单分散胶体在具有和不具有基质扩散的合成单一裂缝中的行为来验证MTDRW方法。（ii）合成的，具有不可渗透基质的单一裂缝中的多分散胶体；（iii）在不渗透的合成裂缝网络中的单分散胶体。在所有这三种情况下，MTDRW方法都复制了单个裂缝中的解析解和裂缝网络中的半解析解的结果。由于MTDRW方法能够模拟整个网络中的物理化学异质性，因此有望提高胶体运输模型的可靠性。（i）评估含水层对胶体迁移的脆弱性；（ii）预测污染事件下的含水层弹性；（iii）制定有效的计划，管理和补救策略。